Data transmission/reception systems for electro-hydraulic control systems

Abstract

A data transmission/reception system usable for bi-directional data transmission in electro-hydraulic control systems between two adjacent supports of a mine installation which each have their own transmitting and receiving stations in a control unit. Bi-directional data exchange takes place via a single wire data bus which is used for simultaneous transmission and reception and forms the summation point for adding the transmitted signals from two transmitters. Each transmitting and receiving station is provided with a subtraction circuit connected to a receiver of the respective transmitting and receiving stations and to which the transmitted signals from its own transmitter are supplied in each case at the subtraction circuit input. The other input of the subtraction circuit is connected to the bi-directional data bus. In this way, a duplex connection between the two transmitting and receiving stations is created in which the transmitted signals from one transmitter is subtracted from two-way transmissions at the associated receiver.

I claim: 
     
       1. An electro-hydraulic control system comprising control units associated with roof supports, said control units serving to actuate electro-magnetic valves and being arranged in groups with each group of control units allocated to several adjacent supports having an intrinsically safe D.C. electrical energy source associated therewith, microcomputer-controlled data transmission and reception stations which are associated with the control units, a bi-directional data bus interconnecting adjacent pairs of the transmission and reception stations and a partial-bus which overlaps the transmission and reception stations of the groups of the control units and forms a further data channel with which the transmission and reception stations of the control units of the relevant group are coupled for data communication; wherein the bi-directional data bus is a single-wire data bus for simultaneous transmission and reception of data between the transmission and reception stations of an adjacent pair of said control units and forms a summation point for the addition of the transmission signals of the stations, each of the transmission and reception stations is provided with a subtraction circuit with an output connected to the receiver of the relevant transmission and reception station, a first input to which the transmission signals of the transmitter of the relevant transmission and reception station are conveyed and a second input connected to the bi-directional data bus. 
     
     
       2. A control system according to claim 1, wherein the transmission and reception stations are provided with summation resistors to establish connection with the bi-directional data bus and the transmitters of the stations are connected via level-adaptation circuits to the inputs of the subtraction circuits. 
     
     
       3. A control system according to claim 1, wherein an impedance converter is associated with the transmitters of the transmission and reception stations. 
     
     
       4. A control system according to claim 1, wherein the partial-bus is connected via a resistor to an electrical reference voltage and each of the control units is provided with a switch with which the partial-bus can be connected to a common reference potential at the commencement of the transmission of data from one of the control units. 
     
     
       5. A control system according to claim 4, wherein the control units each have a comparator which measures the potential on the partial-bus, the comparator being connected on the input side to the partial-bus and on the output side directly and also via a time delay element with the microcomputer of the associated control unit. 
     
     
       6. A control system according to claim 4, wherein said switch is an electronic switch which supplies the transmission data to the partial-bus. 
     
     
       7. A control system according to claim 1, wherein the bi-directional data-bus interconnects the control units in a group-overlapping manner while the partial-bus only extends over the relevant groups which are galvanically separated from one another. 
     
     
       8. A control system according to claim 7, wherein the bi-directional data bus is coupled via isolating means at the transitions between the groups of control units. 
     
     
       9. A control system according to claim 1, wherein the bi-directional data bus, the partial-bus and power supply conductors are united as the cores of a multi-core cable.